1. Field of the Invention
The present invention relates to a lens assembly of a camera module, and more particularly, to a lens assembly of a camera module, which can be mounted in a small portable device such as a mobile communication terminal.
2. Description of the Related Art
Recently, a small camera module has been applied to a portable mobile communication device such as a camera phone, a personal digital assistant (PDA) and a smart phone, and a variety of information technology (IT) devices. As those devices become smaller and slimmer, the camera module is also being miniaturized.
The camera module includes an image sensor as a main component, such as a charge coupled device (CCD) or a complementary metal-oxide semiconductor (CMOS). The image sensor captures an image of an object, and image data is stored on a memory of a device. The stored data is output as an image through a display medium such as a liquid crystal display device (LCD) in a device or a monitor of a personal computer (PC).
A high-performance camera module having an auto-focus function, a zoom function and the like is being mounted in a small electronic device such as a mobile communication terminal.
FIGS. 1 and 2 illustrate a zoom lens barrel assembly employed in a related art digital camera device. Limitations in miniaturizing the camera module being mounted in the small portable device can be described using the zoom lens barrel assembly although they may be considered different in terms of an invention field.
The zoom lens barrel assembly of the related art digital camera device is disclosed in Korean Patent Publication No. 2007-0121304.
As shown in FIGS. 1 and 2, the zoom lens barrel assembly mounted in the related art digital camera device includes a movable lens group 102 including a lens 200, a clip mechanism 212, and a lead screw 116.
Holes 202 and 203 are formed at one side of the movable lens group 102. A shaft 112 is inserted in the holes 202 and 204 to guide the movable lens group 102 in an optical axis direction.
The clip mechanism 212 is coupled to a clip coupling part 208, and a screw coupling part 308 is coupled with the lead screw 116.
A screw thread 214 is formed on the screw coupling part 214 to be engaged with the lead screw 116.
As shown in FIG. 2, a torsion spring 216 is inserted in spring guide walls 302 formed at the clip mechanism 212. The torsion spring 216 has one foot 217 supported by an inner end of the clip coupling part 208, and the other foot 215 supported by a boss 306 of the clip mechanism 215. Thus, the screw coupling part 308 is tightly attached to the lead screw 116 by an elastic force of the torsion spring 216.
The torsion spring 216 of the lens barrel assembly of FIGS. 1 and 2 provides an elastic force to firmly engage the clip mechanism 212 with the lead screw 116. For this reason, without the torsion spring 216, lens driving may be impossible. Thus, the torsion spring 216 may be considered essential for driving of the lens barrel assembly.
In the case of the lens barrel assembly used in the digital camera device of FIGS. 1 and 2, there is no need to miniaturize the torsion spring 216 because the digital camera device has a much greater size than a camera module mounted in a mobile communication terminal or the like. However, to manufacture a similar lens barrel assembly for the camera module of the mobile communication terminal, a torsion spring needs to be very small because of such a small size of the camera module.
For smaller mobile communication terminals, it is necessary to use smaller torsion springs. In this case, the torsion springs become so small that they cannot be observed with the naked eye.
However, it is impossible to manufacture such small torsion springs. Even if it is possible, the torsion springs fail to provide a sufficient elastic force.
Therefore, there is a need for a camera module that can be miniaturized and drive a lens without a torsion spring.